TWI422197B - Transmitter architecture of mimo-ofdm systems capable of reducing peak-to-average power ratio - Google Patents
Transmitter architecture of mimo-ofdm systems capable of reducing peak-to-average power ratio Download PDFInfo
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Description
本發明係有關於一種多輸入多輸出正交分頻多工系統(MIMO-OFDM)之傳送端架構,特別係有關於一種可降低峰值對平均功率比值之MIMO-OFDM傳送端架構。The present invention relates to a transmission end architecture for a multiple input multiple output orthogonal frequency division multiplexing system (MIMO-OFDM), and more particularly to a MIMO-OFDM transmission end architecture that can reduce the peak to average power ratio.
在無線通訊技術中,使用空頻編碼(Space Frequency Block Coding,SFBC)之多重輸入多重輸出(Multiple-input Multiple-output,MIMO)的正交分頻多工(orthogonal frequency division multiplexing,OFDM)系統是相當重要的技術之一,然而,其實際應用上卻存在峰值對平均功率比值(peak-to-average power ratio,PAPR)過高的問題,而PAPR過高係會導致系統功率效益降低、增加裝置耗電及造成訊號失真。為了解決上述問題,習知已有提出以選擇映射法(selected mapping,SLM)降低PAPR,如第1圖所示,其係將調變(modulation)後的符元(symbol),排列在每個子載波上傳送,複製P 組,並分別乘上一隨機相位旋轉向量R 後,經過SFBC編碼器,再通過反快速傅立葉轉換(inverse fast Fourier transform,IFFT)運算後,得到時域上的候選訊號,而不同的隨機相位旋轉向量可以得到不同的候選訊號,再從該些候選訊號中找出一具有最小PAPR的訊號傳送,習知選擇映射法雖可有效降低PAPR,但其所需運算複雜度過高,如在M 根天線的傳送端架構下欲產生P 個候選訊號,就需要MP 個反快速傅立葉轉換運算,其難以實際應用於現今系統中。In the wireless communication technology, an orthogonal frequency division multiplexing (OFDM) system using multiple frequency-input multiple-output (MIMO) using Space Frequency Block Coding (SFBC) is One of the most important technologies, however, there is a problem that the peak-to-average power ratio (PAPR) is too high in practical applications, and the PAPR is too high, which leads to a decrease in system power efficiency and an increase in the device. Power consumption and distortion of the signal. In order to solve the above problem, it has been proposed to reduce the PAPR by using a selective mapping (SLM). As shown in FIG. 1, it is to arrange the symbols after modulation in each subcarrier. After transmitting, copying the P group, and multiplying the random phase rotation vector R by the SFBC encoder, and then performing the inverse fast Fourier transform (IFFT) operation, the candidate signals in the time domain are obtained, and Different random phase rotation vectors can obtain different candidate signals, and then find a signal transmission with the smallest PAPR from the candidate signals. Although the conventional selection mapping method can effectively reduce the PAPR, the required computational complexity is too high. If P candidate signals are to be generated under the transmission end architecture of the M antennas, MP inverse fast Fourier transform operations are required, which is difficult to practically apply in today's systems.
本發明之主要目的係在於提供一種可降低峰值對平均功率比值之MIMO-OFDM傳送端架構,其包含一空頻編碼單元、一訊號產生單元、一循環位移和旋轉相位單元、一訊號向量相加器、一天線訊號產生器以及一比較器,該訊號產生單元係連接該空頻編碼單元,該循環位移和旋轉相位單元係連接該訊號產生單元,該訊號向量相加器及該天線訊號產生器係連接該循環位移和旋轉相位單元,而該比較器係連接該訊號向量相加器及該天線訊號產生器,本發明係利用該訊號產生器之U 個長度為N /U 點的反快速傅立葉轉換器產生出M根傳送天線的訊號,再利用重複的特性將N /U 長度的時域訊號向量複製出完整長度為N 的子載波群向量,並藉由該循環位移和旋轉相位單元改變訊號相位,最後將U 個不同的子載波群重新組合出各天線所需傳輸的資料向量,如此,將可使得運算量大幅減少,本發明在功效上除了可降低PAPR外,亦可大幅降低運算複雜度。The main object of the present invention is to provide a MIMO-OFDM transmission end architecture capable of reducing a peak-to-average power ratio, comprising a space frequency coding unit, a signal generation unit, a cyclic shift and rotation phase unit, and a signal vector adder. An antenna signal generator and a comparator, the signal generating unit is coupled to the space frequency encoding unit, the cyclic shift and rotational phase unit is coupled to the signal generating unit, the signal vector adder and the antenna signal generator Connecting the cyclic shift and rotation phase unit, wherein the comparator is connected to the signal vector adder and the antenna signal generator, and the present invention utilizes U -length inverse fast Fourier transform of the signal generator with a length of N / U points The device generates the signals of the M transmitting antennas, and then uses the repeated characteristics to copy the N / U length time domain signal vector to the full length N subcarrier group vector, and changes the signal phase by the cyclic shift and the rotating phase unit. Finally, the U group of different sub-carriers recombine a vector data necessary for each transmission antenna, thus, will be such that the amount of calculation Width reduction, in addition to the present invention can reduce PAPR, but also significantly reduce the computational complexity on the efficacy.
請參閱第2圖,其係本發明之一較佳實施例,一種可降低峰值對平均功率比值之MIMO-OFDM傳送端架構係包含一空頻編碼單元10、一訊號產生單元20、一循環位移和旋轉相位單元30、一訊號向量相加器40、一天線訊號產生器50以及一比較器60,在本實施例中,該訊號產生單元20係連接該空頻編碼單元10,且用以產生U個的向量,該訊號產生單元20係包含有U個反快速傅立葉轉換器21、(U-1)個向量乘法器22及一訊號分部與係數相乘複製器23,在本實施例中,各該反快速傅立葉轉換器之長度係為N/U,而U及N皆為2的幂次方,此外,(U-1)個向量乘法器22係分別連接(U-1)個反快速傅立葉轉換器21,而該訊號分部與係數相乘複製器23係連接(U-1)個向量乘法器22,此外,在本實施例中,該訊號分部與係數相乘複製器23亦連接第一個反快速傅立葉轉換器21,請再參閱第2圖,該循環位移和旋轉相位單元30係連接該訊號產生單元20之該訊號分部與係數相乘複製器23,其係用以改變該訊號分部與係數相乘複製器23輸出訊號之相位,又,在本實施例中,該訊號向量相加器40及該天線訊號產生器50係連接該循環位移和旋轉相位單元30,而該比較器60係連接該訊號向量相加器40及該天線訊號產生器50。Referring to FIG. 2, which is a preferred embodiment of the present invention, a MIMO-OFDM transmission end architecture capable of reducing a peak-to-average power ratio includes a space frequency coding unit 10, a signal generation unit 20, a cyclic shift, and The rotation phase unit 30, a signal vector adder 40, an antenna signal generator 50, and a comparator 60. In this embodiment, the signal generating unit 20 is coupled to the space frequency encoding unit 10 and used to generate the U. One The signal generation unit 20 includes U inverse fast Fourier transformers 21, (U-1) vector multipliers 22, and a signal division and coefficient multiplying replicator 23. In this embodiment, each The length of the inverse fast Fourier transformer is N/U, and U and N are both powers of 2, and in addition, (U-1) vector multipliers 22 are connected to (U-1) inverse fast Fouriers respectively. The converter 21 is connected to the coefficient multiplying replicator 23 by (U-1) vector multipliers 22. Further, in the present embodiment, the signal section is connected to the coefficient multiplying replicator 23. The first inverse fast Fourier transformer 21, please refer to FIG. 2 again. The cyclic displacement and rotational phase unit 30 is connected to the signal segment of the signal generating unit 20 and the coefficient multiplying replicator 23, which is used to change The signal segment and the coefficient multiplier replicator 23 output the phase of the signal. Further, in the present embodiment, the signal vector adder 40 and the antenna signal generator 50 are coupled to the cyclic displacement and rotational phase unit 30, and The comparator 60 is connected to the signal vector adder 40 and the antenna signal generator 50.
關於本發明之傳送端架構的工作原理係詳細說明如下。考慮一個SFBC MIMO-OFDM系統有M 根天線與N 個子載波,每U 個子載波組成一個頻域子區塊(Subblock),每個頻域子區塊包含Q 個調變符碼,因此編碼矩陣s 可寫成一個M ×U 的矩陣:The working principle of the transmitting end architecture of the present invention is described in detail below. Considering that an SFBC MIMO-OFDM system has M antennas and N subcarriers, each U subcarrier constitutes one frequency domain subblock (Subblock), and each frequency domain subblock contains Q modulation codes, so the coding matrix s Can be written as a matrix of M × U :
其中among them
而μ m , u , q 與v m , u , q 為複數值(complex value),m =1,2,...,M ,且X [q ]是頻域子區塊中第q 個調變符碼。若要完整的考慮各個頻域子區塊的編碼,其係可改寫成And μ m , u , q and v m , u , q are complex values, m =1, 2,..., M , and X [ q ] is the qth tone in the frequency domain sub-block Variant code. To fully consider the coding of each frequency domain sub-block, its system can be rewritten into
其中b 係為頻域子區塊的索引(index),且b =0,1,...,N /U -1,因此第m 根傳送天線向量可表示為Where b is the index of the frequency domain sub-block, and b =0, 1, ..., N / U -1, so the mth transmit antenna vector can be expressed as
,在本實施例中,為了得到時域上超取樣(over-sampling)後的訊號,其係將中間加入(L -1)‧N 個0,以組成一1×LN 的向量,表示如下In this embodiment, in order to obtain an over-sampling signal in the time domain, the system adds ( L -1) ‧ N 0s to form a vector of 1 × LN , which is expressed as follows
其中L 為超取樣(over-sampling)倍數,N 為子載波個數。利用在時域上去取代頻域上運算的技巧,來解決高運算複雜度上的問題,而在時域上對訊號作模數N循環位移m 個單位,即,可發現在頻域上的子載波訊號將會呈現累進旋轉角度效果的相位旋轉,並且不會使訊號的能量改變,其中的表示方式如,m =0,1,…,N -1。在本實施例中,兩個時域訊號向量分別為和x p , q ,而其各自經過離散傅立葉轉換後的頻域訊號向量分別為和X p , q ,且彼此間關係如X p , q =,當乘上一個常數係數r 時,x p , q 相對應的需要乘上一個常數係數r *,才能維持相對的關係。又,在本實施例中,其係將N 個子載波分成U 群,且在系統分離出的向量後,該循環位移和旋轉相位單元30係分別對進行c u , p 的循環位移量與乘上r u , p 的旋轉相位,以得到P 組不同相位的訊號,其中可有效節省複數乘法器,另外,當c u , p =0與r u , p =1時,即代表未作相位旋轉之原始傳輸的天線訊號向量。最後,請參閱第2及3圖,利用該天線訊號產生器50將U 個不同的向量重新組合出各天線所需傳輸的資料向量,在本實施例中,第m 根天線的第p 組候選訊號可表示為Where L is an over-sampling multiple and N is the number of subcarriers. Using the technique of replacing the operation in the frequency domain in the time domain to solve the problem of high computational complexity, and in the time domain, the modulus of the signal is cyclically shifted by m units, that is, , it can be found that the subcarrier signal in the frequency domain will exhibit a phase rotation of the progressive rotation angle effect, and will not change the energy of the signal, wherein Representation , m =0,1,..., N -1. In this embodiment, the two time domain signal vectors are respectively And x p , q , and their respective frequency domain signal vectors after discrete Fourier transform are And X p , q , and the relationship between them such as X p , q = , when When multiplied by a constant coefficient r , the corresponding requirement of x p , q is multiplied by a constant coefficient r * to maintain the relative relationship. Moreover, in this embodiment, the N subcarriers are divided into U groups and separated in the system. After the vector, the cyclic displacement and rotational phase unit 30 are respectively Perform cyclic displacement of c u , p and multiply the rotational phase of r u , p to obtain signals of different phases of P group ,among them The complex multiplier can be effectively saved. In addition, when c u , p =0 and r u , p =1, it represents the antenna signal vector of the original transmission without phase rotation. Finally, please refer to Figures 2 and 3, using the antenna signal generator 50 to make U different vectors. The data vector to be transmitted by each antenna is recombined. In this embodiment, the p- th candidate signal of the mth antenna can be expressed as
且的第n 個元素可以Eq(1)表示如下:And The nth element can be represented by Eq(1) as follows:
本發明主要利用該訊號向量相加器40進行向量的線性組合來產生第一根天線所需傳送的訊號向量,而該天線訊號產生器50則用以產生第二根天線至第m 根天線的訊號,該比較器60則用以比較候選訊號之PAPR,並選出具有最小PAPR之後選訊號。The present invention mainly utilizes the signal vector adder 40 for The linear combination of vectors generates a signal vector to be transmitted by the first antenna, and the antenna signal generator 50 generates a signal from the second antenna to the mth antenna, and the comparator 60 compares the candidate signals. PAPR, and select the signal number after the minimum PAPR.
本發明係利用該訊號產生器20之U 個長度為N /U 點的反快速傅立葉轉換器21產生出M根傳送天線的訊號,再利用該訊號分部與係數相乘複製器23將N /U 長度的時域訊號向量複製出完整長度為N 的子載波群向量,並藉由該循環位移和旋轉相位單元30改變訊號相位,最後將U 個不同的子載波群重新組合出各天線所需傳輸的資料向量,如此,將可使得運算量大幅減少,本發明在功效上除了可降低PAPR外,亦可大幅降低運算複雜度。The present invention utilizes the signal generator 20 of the U of length N / U point inverse fast Fourier converter 21 generates a signal of the M transmit antennas, the reuse factor is multiplied with the division signal duplicator 23 N / The U- length time domain signal vector copies a subcarrier group vector of complete length N , and changes the signal phase by the cyclic shift and rotation phase unit 30, and finally recombines U different subcarrier groups into each antenna. The transmitted data vector, in this way, can greatly reduce the amount of computation. In addition to reducing the PAPR, the present invention can greatly reduce the computational complexity.
本發明之保護範圍當視後附之申請專利範圍所界定者為準,任何熟知此項技藝者,在不脫離本發明之精神和範圍內所作之任何變化與修改,均屬於本發明之保護範圍。The scope of the present invention is defined by the scope of the appended claims, and any changes and modifications made by those skilled in the art without departing from the spirit and scope of the invention are within the scope of the present invention. .
10...空頻編碼單元10. . . Space frequency coding unit
20...訊號產生單元20. . . Signal generating unit
21...反快速傅立葉轉換器twenty one. . . Anti-fast Fourier converter
22...向量乘法器twenty two. . . Vector multiplier
23...訊號分部與係數相乘複製器twenty three. . . Signal division and coefficient multiplier replicator
30...循環位移和旋轉相位單元30. . . Cyclic displacement and rotational phase unit
40...訊號向量相加器40. . . Signal vector adder
50...天線訊號產生器50. . . Antenna signal generator
60...比較器60. . . Comparators
第1圖:習知選擇映射法之傳送端架構示意圖。Figure 1: Schematic diagram of the transmit end architecture of the conventional selection mapping method.
第2圖:依據本發明之一較佳實施例,一種可降低峰值對平均功率比值之MIMO-OFDM傳送端架構示意圖。2 is a schematic diagram of a MIMO-OFDM transmission end architecture capable of reducing a peak-to-average power ratio according to a preferred embodiment of the present invention.
第3圖:依據本發明之一較佳實施例,天線訊號產生器之構造示意圖。Figure 3 is a block diagram showing the construction of an antenna signal generator in accordance with a preferred embodiment of the present invention.
10...空頻編碼單元10. . . Space frequency coding unit
20...訊號產生單元20. . . Signal generating unit
21...反快速傅立葉轉換器twenty one. . . Anti-fast Fourier converter
22...向量乘法器twenty two. . . Vector multiplier
23...訊號分部與係數相乘複製器twenty three. . . Signal division and coefficient multiplier replicator
30...循環位移和旋轉相位單元30. . . Cyclic displacement and rotational phase unit
40...訊號向量相加器40. . . Signal vector adder
50...天線訊號產生器50. . . Antenna signal generator
60...比較器60. . . Comparators
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TW200539601A (en) * | 2004-05-20 | 2005-12-01 | Ind Tech Res Inst | Method and apparatus for papr reduction of an OFDM signal |
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EP1909447A1 (en) * | 2006-10-03 | 2008-04-09 | Lucent Technologies Inc. | Peak-to-average power reduction technique |
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溫志宏、鄭竹軒,在正交分頻多工系統中使用數據循環及邊際資訊***技巧之選擇性映射PAPR 降低方法之研究,(2007/07 公開) * |
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